Peristalsis within a gastro-intestinal (GI) tract may transport swallowed food and may aid in digestion and eventual evacuation. Peristalsis may result in pressure waves or contractions moving along the GI tract, which may result in the motility of a bolus or other object within the GI tract. The bolus may include an in-vivo imaging device able to acquire and transmit images of, for example, the GI tract while the in-vivo imaging device passes through the GI tract.
Rather than exerting a constant force, peristaltic contractions typically exert an oscillating force on the imaging device. The oscillating force pushes the in-vivo imaging device predominantly forward or in a positive direction (resulting in evacuation); however, local back-currents may pull the device backwards as it passes through the GI lumen. Positive/forward/progressive in the context of a device in the GI tract may mean in a direction along the GI tract from the mouth toward the anus.
Images captured while the imaging device is traveling in oscillating motion may be disorienting for a viewer, and may mostly include redundant image information, which may cause un-necessary long image streams. These images may also cause errors in automated tracking or processing systems. For example, when calculating a path-length traversed by the device, current systems may detect movement by changes between consecutive image frames. Such systems may be unable to distinguish between forward and backward movement of the imaging device. Such systems may add to the total path-length calculations, not only images captured during forward movement, but also images captured during backward movement or repeated forward movement through the same GI section due to back-tracking, thereby incorrectly determining that the imaging device has moved farther than it actually has.
There is a need for a system to accurately distinguish and edit image streams captured during oscillating movement of an in vivo device.